1. Field of the Invention
The present invention relates to a memory apparatus and a data processor including the same, or more particularly, relates to a memory apparatus and a data processor using the same which is capable of relieving partial failures by including a spare circuit.
2. Description of the Related Art
In recent years, such a problem was encountered that the probability of defects in a data processor due to failures in a memory increases, as the highly efficient and functional data processor is realized and thereby the capacity of memory of the data processor becomes larger. Particularly, in the data processor such as a microcomputer in which an operation unit, a control unit and a memory unit of the data processor are installed on a single LSI chip, or a cache memory incorporating microprocessor in which the high speed cache memory is installed on the same LSI as the operation unit, since yield of the memory unit controls yield of the whole LSI as the memory capacity installed on the same LSI increases, as far as the memory yield is not improved the yield of the whole LSI is not improved.
In order to prevent deterioration in yields of the memory unit of the LSI, a technique which incorporates a redundant memory circuit in the LSI as a spare circuit, and replaces a defective circuit with the spare circuit by disconnecting wirings by a polysilicone fuse or laser has been proposed. In a non-volatile memory, a technique which replaces a defective circuit with the spare circuit by setting replacement information in a non-volatile latch without disconnecting the wirings by the polysilicone fuse or laser has been proposed, for example, as "Non-volatile Semiconductor Memory", Japanese Patent Application Laid-Open No. 3-162798 (1991).
Meanwhile, a memory which incorporates a diagnosis circuit for diagnosing failures of the memory and a replacement circuit for replacing the defective portion with a spare circuit in the above-mentioned non-volatile semiconductor memory, operates the chip under a self-testing mode for diagnosis and relieves the defective circuit by the operation of the chip element by setting replacement information in the non-volatile latch is also proposed, for example, as "Non-volatile Semiconductor Memory", Japanese Patent Application Laid-Open No. 3-160696 (1991), "Non-volatile Semiconductor Memory", Japanese Patent Application Laid-Open No. 3-160697 (1991) and "Non-volatile Semiconductor Memory", Japanese Patent Application Laid-Open No. 3-160698 (1991).
A process which includes a spare circuit in a built-in cache of a microprocessor and relieves the defective circuit of the cache by disconnecting the fuse by laser has also been proposed already, and is particularly described, for example, in "System, Process, and Design Implications of Reduced Supply Voltage Microprocessor" by R. Allmonn etc. DIGEST OF TECHNICAL PAPERS, 1990 IEEE ISSCC, February 1990.
In the case of replacing the defective circuit with the spare circuit by the physical processing such as disconnecting the wirings by the polysilicone fuse and laser, the physical processing which is not executed as the usual system operation is necessitated after testing the possibility of relief of the system determined as defects. Also, in case of replacing the defective circuit with the spare circuit by setting replacement information in a non-volatile latch, though an additional cost is low when the non-volatile latch can be constituted as same as the other circuit as disclosed in "Non-volatile Semiconductor Memory" Japanese Patent Application Laid-Open No. 3-162798 (1991), in a system in which the non-volatile memory is not used in a usual operation, the non-volatile memory must be added just for the purpose of relieving the defective circuit. Particularly, when manufacturing a non-volatile memory or a data processor installed on a single LSI, a special process for installing the non-volatile latch must be added.
In a conventional process of replacing the defective circuit with the spare circuit by the physical processing, it was necessary to take treatment externally other than the usual operation for diagnosing the failures and replacing the defecting circuit with the spare circuit. In the case of using the non-volatile latch, since replacing information of the non-volatile latch for replacing the defective circuit with the spare circuit is also erased when rewriting data stored in the non-volatile latch by irradiating ultraviolet rays, it is always necessary to switch to a self-testing mode for the diagnostic operation and failure relief operation after erasing the memory content. And hence, a system with no failure at all and a system in which the defective circuit is relieved by the spare circuit must be treated somewhat differently in the manufacturing process or in use, and the two systems could not be treated equally.